First Author:   Alexandru Minea LEO, University of Orléans alexandru.minea@univ-orleans.fr         Second Author: Patrick Villieu LEO, University of Orléans patrick.villieu@univ-orleans.fr         Third Author: Christophe Rault LEO, University of Orléans christophe.rault@univ-orleans.fr         http://membres.lycos.fr/chrault/